The present invention is related to antenna systems for use with wireless radio modems that may be used to provide a communication link for mobile computers.
The demand for use of data processing equipment continues to increase, including demand for not only desktop personal computers but also portable laptop computer and Personal Digital Assistant (PDA) devices. One undeniable trend in the proliferation of small data processing devices is the need to interconnect them—and the public increasingly desires to have the option of connecting them through wireless network devices. Certain of these devices make use of the existing cellular telephone network and a specialized radio modem that applies cellular compatible modulation to the baseband data signals. A number of existing and proposed systems, such as Cellular Digital Packet data (CDPD), General Purpose Radio Systems (GPRS), and even proposed data features of so-called Third Generation (3G) systems, are expected to provide this functionality.
Wireless local area networks (WLANs) however promise to be the most widely adopted type of wireless communication system. In this arrangement, each mobile computer typically uses a wireless modem card that can be in the format of the common Personal Computer Memory Card International Association (PCMCIA) interface. These credit card-size devices can be easily inserted into standardized slots placed in laptop and other portable computing equipment. Such PCMCIA cards then act as Network Interface Cards (NICs) to permit connection in a WLAN, such as to other, similarly equipped peer devices, or to a central wireless Access Point (AP), that may act as a gateway to other networks (e.g., to a wired connection to the Internet).
The most popular WLAN devices operate according to the various standards promulgated by the Institute of Electrical and Electronic Engineers (IEEE) as so-called “802.11a”, “802.11b”, “802.11g”, “WiFi” and similar equipment. Such equipment is permitted to operate in the United States in unlicensed radio frequency bands at 2 GigaHertz (GHz) and 5 GHz ranges—and therein lies the reason why such devices are so popular. There is no need to configure or to pay monthly subscription fees to private service provider in order to obtain wireless data connectivity with WLAN devices.
PCMCIA cards used for WLAN communications necessarily include radio transmitters, radio receivers, modem processors, and other circuits needed for wireless communication, as well as some sort of antenna. Some of the available antenna configurations are quite compact, but most omni-directional in their operation and permanently attached to the PCMCIA card.
Other antenna mechanisms exist in wireless modem configurations. However, these mechanisms typically control only a portion of, for example, a connection of a single transceiver to one of two antenna elements. Each of these antenna elements is simply an omni-directional element and not adapted to provide directionality or increased interference rejection.